[U-Boot] SD card building

[JYOTI DUBEY]

I want to boot a fresh nitrogen6x board with uboot which I compiled
recently.After a successful compilation I obtained u-boot.imx file which I
wanted to bunn on my SD card for booting.
I used "dd if=u-boot.imx of=/dev/sdb bs=1k seek=1" copy u-boot.imx file on
the SD card which gave me the following output
327+0 records in
327+0 records out
334848 bytes (335 kB) copied, 0.00272321 s, 123 MB/s
>>sync
but actually nothing is getting Copied in the SD card. Also there are no
hidden file.
What can be the solution for this.

Thanks in Advance!